The present invention relates to apparatus for processing photographic imaging sheet materials, and is particularly useful for developing so-called "wash-off" photographic products generally comprising a base film or sheet having a coating thereon of photographically active composition which upon exposure to light is preferentially removable from the base subsequent to the application of an activator or developing fluid composition.
The processing of these wash-off products to develop latent photographic images may be readily accomplished manually by the simple application of an activator solution in which either the light-exposed or -unexposed areas of the photographic composition are more readily soluble, and then flushing the solublized material from the surface of the base film. During the manual processing of wash-off products the progress of the development and removal of image-defining portions of the coated composition may be visually monitored. More or less agitation of the developer fluid at the surface of the sheet may be effected to ensure a consistent degree of development over the whole of the image sheet. A rinse or flushing of the surface of the sheet material to remove remnants of partially dissolved or softened imaging composition usually finishes the processing; however, activator solution may be reapplied wherever image development is less than complete.
Such manual developing is normally sufficient for limited scale production of wash-off image sheets of small or medium size, such as may be encountered in some graphic art shops. More extensive production, however, of the larger engineering drawings or graphic arts reproductions has made necessary the use of automatic processing equipment which can ensure a consistency of development and composition removal over the entire surface of such expansive photographic sheets. It is in such use for the processing of large scale, high quality wash-off photographic reproductions that the apparatus of the present invention is particularly advantageous.
This apparatus finds utility in the development of photographic materials based on photoresist or phototech compositions, for example those employing various photopolymer resin coatings. The apparatus is, in fact, particularly adapted to the development of graphic arts reproduction material comprising a coated surface which is in part soft and tacky in its end use, for example as an imaged receptor of dry, colored pigments or powders in a process for preparing a colorproofing sheet. In one such process a photoresist material, preferentially solublized by the exposure to imaging light, is removed in a wash-off procedure to yield an underlying image of tacky polymeric material which will ultimately receive and adherently retain a powdered toner or colorant of a desired primary color. This process further includes a second wash-off development step after the application of such dry colorants and thus requires that the processing be not excessively harsh lest the colorant image be damaged or distorted.
The consistency of the development processing of photographic materials is also a prime requisite in the graphic arts industry, particularly in the art of colorproofing where the integrity of screen patterns must be retained throughout the multiple reproductions comprising a single composite surprint proof. Such processing must not only ensure a constant degree of activator or developer concentration level over the entire sheet surface, but must also avoid physical distortion not uncommonly encountered in previously available processing apparatus.
One such system, as described in U.S. Pat. No. 3,630,213, proposed the transport of a photographic sheet material through a pool of activator solution collected in the valley of a sagging transport belt with subsequent removal of dissolved or softened coated material under the force of rinsing sprays. Although in concept this system would avoid physical contacts with the processing photographic composition, it was practically limited in effectiveness due to the uneven distribution and concentration of developing solution over the surface of the image sheet with resulting imbalance in image density. The difficulties normally encountered in maintaining a consistent tracking of transport belt further detracted from the practicality of this developing apparatus. The high velocity laminar flow of developer solution in a system as described in U.S. Pat. No. 3,791,345 also fails to provide a uniform degree of developer activity across the whole of a larger reproduction sheet.
In contrast to photographic sheet processing equipment heretofore available, the apparatus of the present invention provides for maintenance of a constant concentration of developer over the entire surface of the processing sheet material and affords a constant degree of non-mechanical agitation which ensures the loosening and removal of softened or dissolved photographic coating material without danger to delicate retained surface films or previously applied toning colorants. This apparatus further provides a fluid layer transport system which does not rely upon difficulty controlled belts or similar moving surfaces.